This is a basic stacked-tube-blowback (STBB) to pump conversion tutorial. This conversion should work with any STBB including Spyders, Brass Eagles, Piranhas, ZAPs and Draguns. Although I haven't done this mod, I've read enough tutorials (listed as references) to figure out what makes the marker work. When finished, your marker should go from this:
to this:

Parts:Completely round valve pin. The easiest to use are Dragun “The One” valve pins and Trilogy Sport Autococker valve pins, but are hard to find. Wulf created one out of a threaded rod from a rifle cleaning kit. Vikingshadow modded the stock valve pin by roughing up the flat areas, covering them with JBWeld, sanding the JBWeld down to match the pin itself, and then lightly polishing the modded pin to allow for smooth travel in the valve body.
Courtesy of Fubarius:
Fully round valve pin on the left, stock valve pin on the right.

Slotted striker. This will have to be cut with a Dremel/rotary tool or milling machine. The slot needs to be long enough to allow for the bolt to slide into a fully uncocked position while the striker is still cocked.
Courtesy of Fubarius:
Slotted striker on top, stock striker on bottom. Note: your slot does not necessarily have to go past the o-ring.

Basic functions:
This section is to explain what each modification does to make the pump marker functional.

Modifying the valve pin. A standard STBB valve pin allows air to flow not only into the bolt, but also allows the air to push the striker back and recock it. Using a completely round valve pin will eliminate the flow of air into the lower tube (blowback), thus keeping the striker from automatically recocking.

Modifying the striker. Cutting a slot into the striker allows the striker and bolt to move independently. First, the bolt will be cocked and uncocked to load the ball into the chamber. This will also cock the striker. Then the pull of the trigger will release the striker even when the bolt is in the forward (uncocked) position. The striker will open the valve (via opening the gap between the valve body and cup seal) and allow the air to flow up through the hole in the top of the valve and into the hole in the bottom of the bolt, thus projecting the paintball out of the barrel.

The pump handle. The pump handle simply allows you to manually recock the bolt without taking your hand off the marker.

Putting it all together:
First, you need to take your marker apart enough to take out the valve pin and striker. Replace the stock valve pin with the completely round one. Then replace the stock striker with the modded one, if you didn't mod the striker that originally came with the marker. After you have reassembled the marker, attach the pump handle and connect the pump arm(s) to the bolt.

There are many ways to create a pump handle. Some people use PVC pipes, cans, or whatever else they have lying around. The cleanest way though is the Trilogy Autococker Pump Conversion Kit from PMP Industries. The pump handle threads into the low pressure chamber (LPC) or front plug opening of most STBBs. Vikingshadow's Spyder Sonix and Fubarius' VL Charger use this method. For home made pump handles, you have two options: under-barrel cocking or barrel cocking. The first method involves the pump handle being located under the barrel, while the second involves some kind of pipe being slipped over the barrel like a sleeve. bequickorbedead uses a combination of the two by attaching rings that slide over the barrel to the top of the pump handle. In his bolt action rifle mod, RTisgood uses the bolt from an actual rifle to move the Spyder bolt and cock and load his marker.

How you attach the pump handle and arm to the bolt is up to you. Some people put a metal plate behind the bolt and connect the pump arms to the plate while others connect the pump arm directly to the bolt with JBWeld or by tapping a threaded hole in the bolt, threading the end of the pump arm, and screwing the arm into the bolt. Here are a few different methods:
~Metal plate:WulfCodymm1014
~Bolted to boltFubarius
~Glued to boltbequickorbedead

(7:11:05 PM) Battlechaser: Did you just slaughter George Clooney and steal his mojo..?

"Death doesn't exist. It never did, it never will. But we've drawn so many pictures of it, so many years, trying to pin it down, comprehend it, we've got to think of it as an entity, strangely alive and greedy."
- from Ray Bradbury's Something Wicked this Way Comes

(7:11:05 PM) Battlechaser: Did you just slaughter George Clooney and steal his mojo..?

"Death doesn't exist. It never did, it never will. But we've drawn so many pictures of it, so many years, trying to pin it down, comprehend it, we've got to think of it as an entity, strangely alive and greedy."
- from Ray Bradbury's Something Wicked this Way Comes

Dang - you beat me to it. I think it's kind of funny that people are starting to use me as a reference, haha! Hey, Mom! Look at me, I'm famous!

One thing you might add is that it's extremely difficult to find a round valve pin. T1 pins are nearly nonexistant anymore - at least in my two weeks of searching I couldn't find any. The Trilogy valve pin does NOT get sold separately - you have to buy a valve (IF you can find it) and it's about 30+ bucks. BTW - the PMP industries doesn't have the valve you mentioned above.

I just modified my valve pin with JB weld. What you need to do is rough up the flat part of the stock valve with some sandpaper - get it good and rough so the stuff will stick to it. Then mix equal parts of the JB Weld - it sets up fast so don't be lazy! Get a relatively good amount on the pin and try to form it somewhat to be round (the better you get it, the less you have to do later.) Wait until it's almost set up completely according to the directions, and then sand it smooth, trying it in your valve to check the fit. Make sure it's not too tight, but not loose either. Then, let it set up the rest of the time and polish it a little bit - not too much because it WILL take off more material.

Nice work!

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Pressing onNever argue with an idiot; they'll drag you down to their level and beat you with experience." ~ Anonymous

XD I made a pump this exact way over a year ago. the thread's somewhere in the custom shop I think.
The way I did my pump arm was easy. a piece of pvc pipe, with one arm on the right side (single detent) and a bolt going through a half backed imagine (so the bolt goes through the imagines bolt holes that are already there) works pretty well too like that (it would work without modifying the body too!)
jb welded the pin and slotted my striker. I had a bit of bounce last time I aired it up a year ago because the jb weld wasn't quite thick enough and I think I still had the oring on too. Took only about one hour to make the whole thing too.

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Quote:

Originally Posted by texastornado from PBN

...i was playin with my buddy once and he told me he couldn't cock his acs which had come uncocked. It turns out his arm had fallen off...